A person who is not only a big mouth, but one that can't stop talking about themselves. Every conversation seems to loop back to 'them'.

Jesse: So, this has been the week from hell.
Chad: Fuuuuck... I've been there, I know what you're going through.
Jesse: Uggghh. My wife threatened to divorce me on Tuesday.
Chad: Oh, I went on a date last week... and she would not put out. Fuck that chick!
Jesse: Then my car's transmission went out.
Chad: Fuuuuck. I had a flat last month. Took AAA almost an hour to fix it.
Jesse: And my dog died.
Chad: Fuuuuuuuck. I know man. I had a goldfish die on me when I was ten.
Jessie: Your fucking goldfish?? You... you are a self-centered metamouth!! My God! Why do I come here every week?? You're the worst shrink I ever had.